It is known to generate hydrogen and oxygen by the use of electrical energy in an electrolysis process in which water or another substance containing both hydrogen and oxygen is subjected to the electrolysis in an electrolysis cell, with or without the aid of further chemical reactions, to produce the hydrogen or oxygen or hydrogen and oxides which are generated instead of gaseous oxygen.
An electrolysis cell for this purpose is generally subdivided into an anode compartment and a cathode compartment by a membrane which is permeable to hydrogen.
The production of hydrogen and oxygen by electrolytic decomposition of water, for example, is a well known practice utilizing the above-mentioned approach.
It is known, in addition, to increase the efficiency of the electrolytic decomposition by a simultaneous chemical reaction which has the function of reducing the voltage required for the decomposition at the anode and hence the current requirements for the decomposition.
When a chemical reaction is to be effected simultaneously with the electrolysis for the purpose described, it is desirable, as much as possible, to provide a reversible chemical reaction so that a portion of the supplied energy is coupled with an endothermic chemical reaction.
For example, in the so-called sulfuric acid hybrid process, the sulfur dioxide is initially reacted anodically to sulfuric acid in accordance with the following equation: EQU 2H.sub.2 O+SO.sub.2 (aq).fwdarw.H.sub.2 +H.sub.2 SO.sub.4 (aq).
The sulfuric acid is them thermochemically transformed in accordance with the following reaction: EQU H.sub.2 SO.sub.4 .fwdarw.H.sub.2 O+SO.sub.2 +1/2O.sub.2.
This process has been found to be advantageous because of its relatively low energy requirements although considerable energy must be expended nevertheless for the vaporization of the water used in the process. In addition it has been found that considerable effort is required to recover the oxygen with high purity from the resulting SO.sub.2 /O.sub.2 mixture.
It is also known to produce hydrogen and oxygen by the electrolytic dissociation technique in which hydrogen is withdrawn form the electrolytic solution under the applied voltage by absorbtion in the cathode. At the anode oxygen is released. Such systems are described, for example, in U.S. Pat. No. 3,874,928 and the German Pat. Document (open application--Offenlegungsschrift) No. 2,003,749.
A reversal of this process is also used for generating electricity and it is also known to provide a cathode with a high surface concentration of hydrogen for the production of gaseous hydrogen. The materials used for the cathode are those like palladium or iron alloys which have a high reversible hydrogen diffusion rate. This process cannot be utilized to obtain efficiently molecular hydrogen as is required when the latter is to be used as an energy carrier.